1. Field of the Invention
The invention relates to a method for producing a semiconductor component having a metallic control electrode, and to a semiconductor component having a metallic control electrode. The metallic control electrode as a gate electrode of a field effect transistor has a narrower gate foot, and a broader gate head, and is typically approximately T-shaped.
2. The Prior Art
In the case of monolithically integrated circuits having field effect transistors, particularly HEMT high-performance field effect transistors, the gate length of the gate as a control electrode is of particular importance. The precise production of very small gate lengths below 300 nm is critical. The material combination of metal of the control electrode and of the semiconductor material is of essential significance on the basis of alloy formation, diffusion, chemical reaction and influence on the semiconductor properties. Frequently, electrode metals that are suitable on Si substrates are not suitable for compound semiconductor materials, particularly GaAs and InP, and vice versa.
Particularly in the case of components on a GaAs substrate, aluminum is advantageous as a gate material, as compared with Ti/Pt/Au control electrodes that are frequently used.
Aluminum possesses particularly great conductivity and forms a connection with the semiconductor material that is particularly stable in the long term, without impairing the properties of the material by means of diffusion.
A control electrode made of aluminum is described in German Patent No. DE 103 04 722 A1, in which aluminum is deposited over the entire area and the gate head is produced by means of subsequent marking and etching from the continuous metal layer. In another lift-off technique that is frequently used, a structure for a gate head is predetermined in a mask. It is advantageous if the gate foot and the gate head are aligned with one another in a self-adjusting manner.
After deposition of the gate metal, at least one temperature treatment at elevated temperature is required. However, it has been shown that with decreasing gate length, the field effect transistors having an Al gate tend to exhibit NOPO (NO Pinch Off) errors, making the components unusable for many applications.